Adaptive Cruise Control (ACC) is a control method for automatically controlling a road vehicle within a lane of traffic, maintaining a desired speed while maintaining a safe distance from other road vehicles in the same lane of travel. The essential function of ACC is target vehicle following which means that a road vehicle hosting the ACC follows a target vehicle while maintaining a predetermined separation (e.g. time or distance). The host vehicle is thus the vehicle being controlled by ACC, and the target vehicle is the vehicle in front of the host vehicle.
The host vehicle includes a device or devices capable of sensing presence, range, and a change in range, i.e. range rate, between the host vehicle and a target vehicle in the same lane of travel. A number of devices or combinations of devices are capable of generating this information, e.g. one or more of a Radio Detection And Ranging (RADAR) sensor, a Light Detection And Ranging (LIDAR) sensor, a Light Amplification by Stimulated Emission of Radiation (LASER) sensor, a SOund NAvigation and Ranging (SONAR) sensor (e.g. ultrasound), an InfraRed (IR) sensor, an image sensor (e.g. camera), vehicle location devices (e.g. GPS) or any combination thereof.
The inputs to control the ACC system within the host vehicle will usually include the sensed range, range rate and the host vehicle speed. Target vehicle following occurs when the ACC processes inputs, according to programming applying a desired range formula, and outputs acceleration commands to brake/throttle control modules according to the sign (i.e. positive acceleration command is sent to throttle control module and negative acceleration, deceleration, is sent to brake control module). The brake and throttle control modules translate the deceleration and acceleration commands into brake and throttle effort and applies brake and throttle accordingly.
Drivability is an important characteristic of a road vehicle operated by ACC. Drivability is adversely affected by quick or frequent changes in acceleration, high jerk, or other dynamic factors that detract from smooth operation of the road vehicle.
An attempt has been made at providing a method and an apparatus for target vehicle following control for adaptive cruise control having improved drivability. This attempt is described by document US 2010198478 A1.
US 2010198478 A1 describes how a host vehicle's speed is controlled with a target vehicle following control system when following a target vehicle. The target vehicle following control system monitors a range with respect to a target vehicle and a speed of the host vehicle. The target vehicle following device determines operation of the host vehicle based upon a control region by comparing the range and the speed of the host vehicle to a simple sliding surface, which defines a minimum range between the host vehicle and target vehicle, and a modified sliding surface, which increases the margin to the simple sliding surface as the speed of the host vehicle increases. A desired longitudinal acceleration/retardation of the host vehicle is determined based on the control region and is subsequently used to control operation of the host vehicle.
However, although the method and an apparatus according document US 2010198478 A1 will provide an increased margin to the simple sliding surface as the speed of the host vehicle increases that provides for improved drivability there is still room for further improved drivability of road vehicles operated by ACC.